In recent years, silver halide photographic light-sensitive materials (hereinafter referred to as "light-sensitive material") have been demanded to be improved in various aspects. What is especially required in the art is a light-sensitive material having a high sensitivity and stable photographic properties, and capable of producing images having good quality and less fogging.
In a light-sensitive material for X-ray, there is a strong demand for high sensitivity and high image quality so that a prescribed level of exposure can be attained with less amount of X-ray in order to minimize an exposure of X-ray to a human body, and for rapid processing in order to obtain the results of an X-ray examination as soon as possible.
Under such circumstances, various proposals including the methods of forming silver halide grains have heretofore been made to provide a light-sensitive material for X-ray photography having a higher sensitivity.
For instance, there is disclosed in Japanese Patent Publication Open to Public Inspection (hereinafter abbreviated as Japanese Patent O.P.I. Publication) Nos. 184142/1983, 19628/1986 and 205929/1986, a method in which a spectral sensitizer is added in the formation of silver halide grains, physical ripening or desalting.
Generally, a light-sensitive material comprising an insulated support and photographic component layers is liable to accumulate static electricity thereon due to friction caused by contact with the same or foreign materials. If accumulated static electricity is discharged before development, a light-sensitive material is exposed to form so-called static marks branch- and featherlike linear spots in development. These static marks impair significantly the commercial value of a light-sensitive material. Static marks appearing on an X-ray photograph for medical or industrial use are very dangerous since they tend to cause fatal misjudgement. The formation of such static marks cannot be found until development, which makes this phenomenon one of the serious problems. In addition, the accumulation of static electricity is liable to cause the secondary problem that it allows dust to adhere to the surface of a film and makes it difficult to carry out uniform coating. The formation of the static marks is expedited by a higher sensitivity, a higher coating speed, a higher Photographing speed and a rapid automatic processing. A light-sensitive material has to inevitably be brought into contact with various instruments such as a roller, or with another light-sensitive material during the production processes including coating, drying, processing and wrapping, or in loading a film, photographing and carrying out automatic development. Such contacts allow static electricity to generate.
In order to improve the conductivity of a support or photographic component layers, various methods have been proposed. These methods include the addition of various hydroscopic substances, water-soluble inorganic salts, a certain kind of a surface active agent, or a polymer.
However, these substances tend to show a specificity and adversely affect the photographic properties depending on a kind of support and photographic components. It is especially difficult to prevent the generation of static electricity in hydrophilic colloidal layers by the above substances. A surface specific resistance is not lowered sufficiently at a low temperature or a high humidity, and there is sometimes caused adhering between the light-sensitive materials themselves or to the other materials at a high temperature and a high humidity. There are many compounds such as polyethylene oxide compounds which have an antistatic effect, while they have adverse effects such as increased fogging, desensitization, deteriorated graininess. It is difficult to find out an antistatic agent which is suited to a light-sensitive material for an X-ray photograph for medical use, which has an emulsion layer on each side of a support.
In the case of the above-mentioned light-sensitive material for X-ray photograph highly sensitized by a spectral sensitizer, there has been found the unexpected problem that the surface specific resistance is increased significantly at a high humidity (humidity: 50% or more).
The conventional antistatic methods have been found to have an effect to some extent, but they are not necessarily satisfactory since they sometimes impair other properties such as sensitization.